The reason why I switched from a centralized to a distributed RCS was
that I really like the option to do (small) local checkins and just do
the "real" checkin when the work is done. In terms of BZR it means
commits to my local branch for smaller changes and pushes back to
the mainline for every major change. Oh, and it's also nice always
having the full repository data locally stored.

My requirements for the RCS were: it should be easy to use (no steep
learning curve), well tested and somewhat mainstream. BZR fits quite
well, especially since Ubuntu heavily relies on it for their launchpad
stuff.

PS: Thanks to the alioth team for creating
the BZR repository so quickly, it just took like 1 minute.